A Stray Robert Louis Stevenson Quote

There is an interesting quote from Robert Louis Stevenson that I've been trying to track down in its original appearance.  I have seen it in various newspapers and magazines in the years following Stevenson's death on the evening of December 3, 1894, in Samoa.  Variously it is attributed (if it is attributed at all) to a Washington correspondent or reporter.  The earliest I have so far traced this is to a newspaper, The Logansport Daily Reporter (of Logansport, Indiana), of Saturday afternoon, January 5, 1895.  I copy the entire brief report here:

Robert Louis Stevenson told a Washington correspondent that his story of "Dr. Jekyl[l] and Mr. Hyde" had for its foundation an incident related to him by a London doctor who made diseases of the brain a specialty. None of his work was absolute fiction, and most of it had a basis in actual experience. "I do not believe," he said, "That any man ever evolved a really good story from his inner consciousness, unaided by some personal experience or incident of life."  

If anyone knows more details, or a fuller version or an earlier appearance of this anecdote, I'd be grateful to learn of it.

Update 1/2/16:  One reader wrote in with some information on "the doctor" in Jekyll and Hyde, not the "London doctor" of the quotation, which I copy below (thanks, Brian!).  I remain primarily interested in the source of the quote (and especially whether there is any more context given, and any further Stevenson comments):

The doctor that Stevenson apparently based aspects of Jeykll/Hyde on is John Hunter, the famous Scottish surgeon, who's personal anatomical collection became the foundation of the famous Hunterian Museum (of the Royal College of Surgeons) in London; the Hunterian Society derives its name from him too. He had an older brother, William Hunter; also a famous Scottish anatomist; he also had a private collection (with books & coins & much else), which went on to form the nucleus of the renowned Hunterian Museum (& Art Gallery) of Glasgow University. Two incredible brothers, from an era of Glasgow/Scottish history that I'm reasonably familiar with.
https://en.wikipedia.org/wiki/William_Hunter_(anatomist)
https://en.wikipedia.org/wiki/John_Hunter_(surgeon)
(I haven't actually read the Wiki articles in detail; the links are just so you know who I'm referring to.)
 
Ian Rankin (the Scottish crime writer) made a documentary (which I didn't actually like very much) which covers the story of Stevenson & Hunter; in particular some aspects of Hunter's London residence, which will be very familiar to anyone who's read Stevenson's Jekyll & Hyde. Some of the details covered in the documentary are dealt with in the following article (from the Guardian, 2010): http://www.theguardian.com/books/2010/aug/16/ian-rankin-dr-jekyll-mr-hyde

Update 6/4/19:  I'm please to note that this conundrum has been solved for me by Garson O'Toole, the Quote Investigator (visit his fascinating website at QuoteInvestigator.com).  The quote comes from a memoir in The Washington Post, 30 December 1894, by someone signed only as "W.H.R." The article is titled "By One Who Knew Him: Interesting Personal Sketch of Robert Louis Stevenson." Unfortunately, some of the details of the anecdotes given about Stevenson are decidedly incorrect, so one must also question how accurately "W.H.R." remembered or recorded things told to him by Stevenson in speech over the course of some thirteen years of occasional acquaintanceship.  The fuller anecdote, as recalled by "W.H.R.," is as follows:

“I do not believe,” said Mr. Stevenson one day, “that any man ever evolved a really good story from his own consciousness, unaided by some personal experience or incident of life as a basis. This work-a-day world is fuller of marvelous happenings than is the workhouse of any human brain. That Jekyll and Hyde tale, had its foundation with the best of it in a curious story told me by a London doctor, who made diseases of the brain a specialty. . . .”

 Now I'm left wondering who this "W.H.R." was?